Cryogenic System for LINAC Superconducting Polarization Solenoid
e-bubble project
Project: Novel Electron Bubble Particle Detector
Procedure for Operating Columbia (Nevis) LHe Electron Bubble Chamber Cryostat
Version 4.0
Hand Processed Changes
HPC No. Date Page No. Initials
Approved: Date:
Procedure for operating Nevis LHe EBC
1. Purpose
1.1 This Operating Procedure Manual provides instructions for operation of the Columbia (Nevis) LHe Electron Bubble Chamber (EBC) System, with explanation of the LHe/LN2 Cryostat and associated infrastructure involved.
1.2 The Operating Procedure set forth here is required for the safety of the system and of the operators. All participants in the operations must study the Operating Procedure Manual.
1.3 The Log Book for operations must indicate which version of the Operating Procedure Manual is being followed at the time; who is in charge of operations at any given time (Chief); and who else is assisting. All significant conditions in the system and changes must be noted in the Log Book.
2. Responsibilities
2.1 It is the Chief operator’s responsibility to ensure that all operators have the appropriate training, and that all procedures in this Manual are followed.
3. Prerequisites
3.1 All operators must have received the required BNL Training prior to working with the LHe EBC system, and have studied this Operating Procedure manual.
4. Precautions
4.1 Be sure that all necessary system components are functioning correctly prior to start-up.
5. Procedure
5.1 Before Start-up
5.1.1 Make sure that the vacuum jacket of the LHe transfer line has been properly evacuated. Periodic re-evacuation of the transfer line jacket is necessary for efficient LHe transfer.
5.1.2 Be sure that all valves (vacuum, ball and globe) except ball valve 16 on the LHe Dewar are closed, and that all relief valves are installed on the LHe Dewar, LN2 Dewar, Pumping port and Cryostat.
5.1.3 Do not open any valves if there is below 0 (psig) pressure indicated on the pressure gauges P4 and P5 on the LHe Dewar and LN2 Dewar. This would allow air to rush into the Dewar and form an ice plug.
5.1.4 Be sure to wear safety glasses and insulated gloves when handling liquid helium and nitrogen.
5.2 Evacuation of LHe/LN2 Cryostat Vacuum Jacket
5.2.1 Connect the flexible coupling from the turbo-pump (TP1) to the connector of vacuum valve 103 extending from the Cryostat.
5.2.2 Open vacuum valve 103 and vacuum valve 101 on the top of turbo-pump (TP1), turn on the turbo-pump, and evacuate the cryostat vacuum jacket until the pressure at the pump drops to 1×10-5 torr or less, as measured by the ionization gauge (TC5). It is recommended to evacuate the system overnight before operating.
5.2.3 Do not introduce cryogen into the chamber with the evacuation valve open. This may cause cryopumping of vacuum pump oils into the Cryostat vacuum jacket.
5.3 Evacuation of central tube and e-bubble chamber
5.3.1 With Cryostat at room temperature, open ball valve 1, 2, 5 and 6 on the control panel and open ball valves 7 and 8, on the top of central tube
5.3.2 Turn on Turbo-pump (TP2) to evacuate the central tube, e-Bubble chamber and gas transfer line until the pressure drops below 10-3 torr (TC2).
5.3.3 Close ball valves 7, 1 and 2.
5.3.4 Turn off Turbo-pump (TP2)
5.3.5 Open globe valve 13 and set regulator valve 12 at 10 psig. Open needle valve 11 and ball valve 9, allowing helium gas into the central tube. After 30 seconds, close ball valve 9, the central tube is now pressurized (10 psig), as measured by pressure transducer (P2) on the top of central tube.
5.3.6 Open ball valve 3 and slightly open ball valve 7, release helium gas out off the central tube, through check valve R12 make sure that the pressure is slightly higher (~1 psig) than atmospheric pressure, then close ball valve 7 and 3.
5.3.7 Repeat the above pump and purge procedures (5.3.4 through 5.3.6) 2~3 times. Stop after step 5.3.5 on the last cycle.
5.3.8 Set regulator valve 12 at required pressure. Open ball valve 9, allowing helium gas into the central tube.
5.3.9 After 30 seconds, close ball valve 9, the central tube and e-Bubble chamber are filled with pressurized pure helium gas.
5.4 Pump/purge LHe vessel and Cooling circuit
5.4.1 Never evacuate the LHe vessel unless the Cryostat vacuum jacket has been previously evacuated, collapse of the LHe vessel wall may occur.
5.4.2 Insert the SS filling tube though helium fill port (C1) into LHe vessel until it reaches the bottom, then seal helium fill port C1.
5.4.3 Connect a Teflon transfer hose to the SS filling tube and connect the other end to the quick connector C19 on the LN2 Dewar.
5.4.4 Open ball valve 1,2 and 4 on the control panel.
5.4.5 Open ball valves 104 and helium needle valve 105.
5.4.6 Turn on Turbo-pump (TP2), to evacuate LHe vessel and flow passage through the needle valve, capillary tube and cooling circuit loops, until the pressure drops below 0.1 torr (TC2) to remove any air or moisture.
5.4.7 Close ball valves 104, 1, 2 and 4, and turn off the Turbo-pump (TP2).
5.4.8 Set regulator valve 12 (on the gHe bottle) at 0.5~1 psig, and open ball valve 10, allowing helium gas into the LHe vessel.
5.4.9 After 30 seconds, close ball valve 10 and helium needle valve 105. The LHe vessel is now pressurized (0.5~1 psig).
5.4.10 Close needle valve 11. Be sure to close ball valve 22 on helium vent port C2 of the LHe vessel to prevent air and moisture from entering the vessel.
5.5 Precooling LHe Vessel with LN2
5.5.1 Open globe valve 20 on the LN2 Dewar, this valve can be adjusted (1/4~1/2 turn) to obtain the proper liquid flow rate.
5.5.2 Open ball valve 22 on the helium vent port (C2). Liquid nitrogen will be transferred into the LHe vessel directly from the pressurized LN2 Dewar.
5.5.3 During this cool down, open occasionally the helium needle valve 105, by approximately 3~5 turns, to let LN2 enter the needle valve, capillary tube, and cooling circuit loops. This procedure also prevents the needle valve from freezing shut as it is being cooled along with the rest of the LHe vessel.
5.5.4 After about 15 min, when T1 on the bottom flange of LHe vessel drops below 81K, it indicates that there are some LN2 cumulated inside LHe reservoir. From then on it takes about 10 min to fill ~10 liters of LN2, which are sufficient to precool LHe vessel.
5.5.5 Close globe valve 20 on the LN2 Dewar.
5.5.6 Wait several minutes to let LN2 calm down, disconnect the Teflon transfer hose from the SS filling tube.
5.5.7 Lift slowly the SS filling tube out off helium fill port (C1) on the LHe vessel, and seal helium fill port (C1) by rubber stopper
5.5.8 Close ball valve 22 on the helium vent port (C2) to prevent air and moisture from entering LHe vessel, LN2 vent out through relief valves R4 (0.5 psig).
5.5.9 Keep the Teflon transfer hose on the quick connector 19 of the LN2 Dewar.
5.6 Liquid Nitrogen Filling to ln2 vessel
5.6.1 Insert the Teflon transfer hose though one of the nitrogen fill/vent ports (A1) into the LN2 Dewar until it reaches the bottom.
5.6.2 Open globe valve 20 on the LN2 Dewar, this valve can be adjusted (1/4~1/2 turn) to obtain the proper liquid flow rate.
5.6.3 LN2 will be transferred into LN2 vessel directly from the pressurized LN2 Dewar, while venting though the other two nitrogen vent ports (A2 and A3).
5.6.4 Approximately 40~45 liters (~30 min) of LN2 is needed for this cool-down and fill.
5.6.5 When the LN2 starts to be visible from one of the nitrogen vent ports (A2 or A3), close globe valve 20 on the LN2 Dewar.
5.6.6 Record readings on temperature T10 and T11 periodically during steps 5.6.3 through 5.7.1.
5.6.7 Remove the Teflon transfer hose from nitrogen fill/vent tubes (A1) on the LN2 vessel and seal it with rubble stopper. Nitrogen vapor will vent through the other two nitrogen vent ports (A2 and A3).
5.7 Lower temperature of e-bubble chamber
5.7.1 Adjust the needle valve operator 105 at the top flange of the cryostat to change the LN2 mass flow rate entering the cooling circuit loops from the LHe vessel.
5.7.2 Open helium needle valve 105 3~8 turns, and open ball valves 3 and 4 on the control panel, in this case helium vapor will vent out directly to atmosphere through check valve R12. The venting flow rate can be monitored either by flow meter FM1 or FM2 on control panel.
5.7.3 Monitor temperature drops of T4, T5, T6, T7, T8 and T9 around the e-Bubble chamber.
5.8 Remove LN2 from LHe Vessel
5.8.1 Wait and allow LN2 to completely cool LHe vessel and e-Bubble chamber to lower than 80K (~several hours) by checking temperature T4, T5, T6 and T9.
5.8.2 Insert the SS filling tube though the helium fill port (C1) into LHe vessel until it reaches the bottom and connect a Teflon tube to it.
5.8.3 Set regulator valve 12 on the gHe bottle at 2~5 psig. Open needle valve 11 and ball valve 10. Admit warm gas helium into the LHe vessel.
5.8.4 Seal relief valves R4 (0.5 psig) by relief valves R5 (4 psig) to allow pressurization
5.8.5 LN2 will start flowing out of this tube once the LHe vessel is pressurized. The LN2 outflow should be transferred to a suitable container (e.g. a bucket).
5.8.6 Continue this process for about 5 minutes until it appears that no LN2 is flowing out off the Teflon tube. Note that solid nitrogen has a very large heat capacity (an order of magnitude greater than copper), so even an inch left at the bottom of the vessel will require large amounts of liquid helium to cool to 4.2K.
5.8.7 Remove the SS filling tube from LHe vessel and seal the helium fill port (C1) by rubber stopper.
5.8.8 Close ball valve 10.
5.8.9 Check temperature T1 and wait until it is higher than 82 K.
5.9 pump/purge LHe Vessel and Cooling circuit
5.9.1 Open ball valve 1, 2, 3 and 4 on the control panel.
5.9.2 Open ball valves 104 and helium needle valve 105.
5.9.3 Turn on Turbo-pump (TP2), to evacuate LHe vessel and flow passage through the needle valve, capillary tube and cooling circuit loops, until the pressure drops below 0.1 torr (TC2) to remove any air or moisture.
5.9.4 Close ball valves 104, 1, 2 and 4, and turn off the Turbo-pump (TP2).
5.9.5 Set regulator valve 12 (on the gHe bottle) at 0.5~1 psig, and open needle valve 11, allowing helium gas into the LHe vessel.
5.9.6 After 30 seconds, close ball valve 10 and helium needle valve 105. The LHe vessel is now pressurized (0.5~1 psig).
5.10 Liquid Helium Filling to lhe vessel
5.10.1 Before LHe transfer, maintain the pressure inside LHe vessel at 0.5 psig by setting regulator valve 12 at 0.5 psig, and keeping valves 10, 11 and 13 open.
5.10.2 Unplug the rubber stopper on the helium fill port (C1), insert quickly the LHe transfer line to the bottom of LHe vessel through the helium fill port (C1) and tighten its connector. At the same time,
5.10.3 Close ball valve 16 on the LHe Dewar, and remove the plug of quick connector 14, open fill valve 15, insert slowly the LHe transfer line into LHe Dewar, until it reach the bottom of the LHe Dewar, and tighten quick connector 14.
5.10.4 Close ball valve 10 and open ball valve 22. The boil-off caused by the warm LHe transfer line being inserted into the LHe Dewar will cause immediate pressure rise and transfer liquid helium into LHe vessel.
5.10.5 Set the initial transfer rate of liquid helium at a very slow rate, by regulating the pressure in the LHe Dewar (in the range 0.5~1 psig). This guarantees that no liquid helium is accumulated in the LHe vessel until T3 at bottom of 4K-heat shield is cooled below 20K.This slow transfer makes more efficient use of the enthalpy of the liquid helium as it cools the LHe vessel and the attached radiation shield.
5.10.6 During LHe transfer, open and close helium needle valve 105 several times, to clear the path through needle valve and capillary tube and let liquid helium enter the cooling circuit loops for e-Bubble chamber cooling.
5.10.7 The venting flow rate can be monitored either by flow meter FM1 or FM2 on control panel.
5.10.8 When T3 at the bottom of the 4K-radiation heat shield has cooled down to approximately 20K, the helium transfer rate can be accelerated a little
5.10.9 Open helium needle valve 105 3~5 turns, and open ball valves 3 and 4 on the control panel, in this case helium vapor will vent out directly to atmosphere through check valve 12
5.10.10 Monitor temperature drops of T4, T5, T6, T7, T8 and T9 around the e-Bubble chamber. When the desired lower temperature has been reached, close ball valve 4 on the control panel
5.10.11 The venting flow rate can be monitored either by flow meter FM1 or FM2 on control panel.
5.10.12 Check the helium level meter occasionally. The LHe vessel is completely filled (21” on the level meter) using ~ 70 liters of liquid helium for cool down and fill.